Air August 25, 2004

Thank you Jerry, and good morning everyone.

Classic hit or miss thunderstorms give blessings to part of the region and leave other areas longing for rain, but certainly not the hail!!

Something is going on in a lot of the corn and sorghum fields. If you haven't noticed it you're either lucky, or not paying attention. Bottom leaves of corn and sorghum plants are turning yellow and then dying. This has started on the bottom most leaves and is slowly working its way up the plant. Sometimes it's just a plant or two, other times it is in a portion of a field and other times the problem is showing up field wide. In some cases, grain sorghum plants are stunted and haven't even headed out yet. The problem is nitrogen deficiency and at this stage of the game, there is little that you can do about it, OTHER than to take notice and make plans for next year. How did we get into this dilemma I have been asked more than once recently. I fertilized at the same rate I have for the past several years. Well the problem started with the 2003 wheat crop. Those absolutely incredible wheat yields a year ago partially came from the plant having good growing conditions which allowed it to scour every bit of nitrogen from the soil. We often assume a little bit of carryover nitrogen, which we didn't have this year. Then we applied most or all of our nitrogen before or at planting time. Then came wet conditions that were perfect to maximize nitrogen fertilizer loss from the soil. We started with less than needed and then lost more than we normally figure on losing. These factors coupled with good early season growing conditions have led to a total consumption of soil nitrogen. So next year, it may be very prudent to sample every field for soil testing and even go through the extra effort to take deep samples. Then let's get aggressive on the nitrogen fertilization plan. A 125 bushel grain sorghum yield goal calls for 150 pounds of nitrogen fertilizer. If you have 5 or 6 ppm of N in the soil you can cut back to 130 pounds and even 10 ppm can allow you to reduce application rates to 100 pounds. But if you assume some carry over and you have none, we'll see a repeat of what we have right now. Even in wheat - a 60 bushel yield goal can require 80 to 120 pounds of nitrogen, depending on your soil test. Sure fertilizer may be expensive, but cheating your crop of the nutrients it needs is expensive too!

This is Chuck Otte, Geary County Extension Agent, with Ag Outlook 2004.

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